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circumpolar constellation
In astronomy, the circumpolar constellations are constellations that never set from the viewer's perspective. Considered a very important effect in astronomy, it is different from seasonal constellations. Circumpolar constellations stay in the sky.
Because of the rotation of the Earth and its orbit around the Sun, we divide the stars and constellations into two groups. Some stars and constellations never rise nor set, and they are called circumpolar. All the rest are divided into seasonal stars and constellations. Which stars and constellations will be circumpolar and which seasonal depends on your latitude. In the northern hemisphere, we will always be able to see stars and constellations in the northern circumpolar sky, while in the southern hemisphere, we will always be able to see stars and constellations in the southern circumpolar sky.
The celestial north pole, currently marked by Polaris, always has an azimuth equal to zero. Also, its altitude for a given place is fixed and its value is given by the following formula: A = 90-Ø. All stars with a declination less than A are not circumpolar.
They are also visible year round at that location. From the North Pole, all constellations north of the celestial equator, (all fully visible constellations) are circumpolar, and similarly from the South Pole. From the equator, there are no circumpolar constellations. From mid-north latitudes (40–50°N), circumpolar constellations may include Ursa Major, Ursa Minor, Draco, Cepheus, Cassiopeia and the not well known Camelopardalis.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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